I feel like my mystery plant is slowly dying :(

I inherited this plant from my grandparents several years ago and therefore don't even know what plant it is (if anyone can help even with that, I'd be grateful!). However, it feels like the longer I have the plant, the worse it is doing. The biggest issue is the tilt: I feel the roots of the plant are not strong (or healthy?) and therefore the weight of the plant is slowly toppling it over. However after I moved half a year ago I feel the plant is also not drinking properly, as now the soil seems to stay wet for long and I feel worried about root rot. The plant is still making new leaves, but they have light spots on them and some of them die straight after emerging.

The living conditions of the victim:
Watering: when the soil is dry, which is between every 1-2 weeks. The plant used to drink a lot, almost a litre at a time. Watered from below, sometimes pouring 1-2dl to the top of the soil as well.
Light: Indoor, not near a window but getting indirect light, BUT living in the Northern hemisphere so very little of it during the winter. Most likely not getting enough light overall, but options for lighting are limited.
Soil: most likely flower soil so dense and bad.

The verdict I seek: what can I do to this poor soul? I have limited time and other responsibilities as well, but I'd like this innocent plant to at least – not die. I can go buy something new to replace the soil with, but don't want to fill my cabinets with dozen different soil materials as I live in an apartment and space is limited. As said before, light options are limited but as a last measure I can move it to a window facing west (not preferring this though).

Thank you for your time and help! 🪴